Use of a common electrolysis apparatus to increase the pH value of water is well known in the art. Generally, electrolysis is a very useful and simple process for separating chemically bonded elements and compounds, which is performed by applying an electric current across a pair of electrodes, anode and cathode, immersed in an electrolyte such as water or aqueous solution. The electrolyte is the medium to conduct electricity as it consists of free ions in solution.
One important application of electrolysis is to produce oxygen and hydrogen by electrolyzing water in an electrolytic cell having a separator arranged between the anode and the cathode. In this case, acid water is produced at the anode and alkaline water is produced at the cathode.
Alkaline water is known to find a wide range of applications. For example, alkaline water is useful for drinking, disinfecting and cleaning, depressing an abnormal intestinal fermentation and the like. Another application is that alkaline water is able to remove toxic components and the greenhouse gases SO2, NOx, and CO2 in a flue gas, because of the high pH value and alkalinity of the alkaline water.
Alkaline water may be produced by the addition of an alkali agent such as NaOH in the water. Alternatively, ion membrane electrolysis of, for example, seawater may be used. However, due to the presence of NaCl, electrolyzing seawater or saline water always results in the generation of chlorine gas at the anode side, which is likely to re-dissolve back in the water treated, and thus decreases the pH value of the water. This consequently affects the rate or performance of generating alkaline water of high pH values. In addition, chlorine gas is known to be harmful to human health and the environment, especially to the organisms living in seawater and soil.
U.S. Pat. No. 6,527,940 discloses a production method of acid water and alkaline water in a water electrolytic cell which is partitioned by a cation-exchange membrane. However, this method requires a membrane of high cost and complicated maintenance work. In the method of this patent, the performance and rate of production of acid water and alkaline water largely depends on the condition of the membrane, and the rate of alkaline water production is reduced if leakage of the membrane used takes place.
U.S. Pat. No. 6,638,364 discloses a cleaning system and method using electrolyzed alkaline water. In this patent, chlorine gas is generated on the anode side when the alkaline water is produced in the direct electrolysis of saline water. As mentioned above, chlorine gas is harmful to the environment and thus unwanted. Another disadvantage of this patent is that the alkaline water may be neutralized because the chlorine gas is re-dissolved back in water.
U.S. Pat. Nos. 4,406,758, 4,457,953 and 4,891,107 also disclose various electrolysis apparatuses having a porous diaphragm and a hydrophobic carbon cathode. These patents are inevitably accompanied with the drawback that the operation of the apparatuses are troublesome because the amount or the rate of movement of the electrolyte solution from the anode chamber to the cathode chamber is difficult to control.
To prevent the generation of chlorine gas, magnesium may be used as the anode to produce magnesium hydroxide which will increase the pH and alkalinity of seawater without the generation of chlorine gas. However, a massive amount of magnesium is needed due to its high consumption rate, thus requiring the constant replacement of the magnesium electrode, which is not desirable.
To avoid the periodical replacement of highly consumable magnesium electrodes, one may choose to use a permanent electrode such as a platinized titanium electrode, metal oxide-coated titanium electrode and the like. Chlorine gas will however be generated when these electrodes are used. Moreover, these permanent electrodes are very expensive.
An inexpensive material is steel. The resiliency, versatility and recyclability of steel make it a very useful basic industrial material on earth today. While there are currently more than 3500 different grades of steel according to the World Steel Association, its use as an electrode in alkali water generators or electrolytic water cells has largely been met with disappointments due to the electrochemical corrosion and erosion of steel and the generation of harmful substances like chlorine and other oxidants when seawater is employed.
The chromium-containing stainless steel is more corrosion-resistant and less-consumable, but it has also been shunned by industries for use in such devices since the chromate waste additionally produced becomes a serious environmental hazard.
Therefore, there exists a need for both a new apparatus and a method for producing high pH alkaline water by use of the electrolysis process, which are inexpensive, easy and convenient to control and causes no harm to the environment and the people.